The disclosure regards a system and a method capable of functioning as an apparatus for transport and handling of equipment in a lifting arrangement used on a floating vessel. More precisely, the disclosure regards a method and an apparatus for rigging up intervention equipment in a lifting arrangement utilized on a floating vessel, and moving the intervention equipment between an inoperative and an operative position.
Offshore subsea wells are typically developed using floating vessels to accommodate equipment, personnel, and operations necessary to drill and complete a well in order to initiate production of hydrocarbons from a given reservoir forming the target for the well. Additionally, testing and intervention work is typically executed through the use of such floating vessels. It is to be understood, however, that such a floating vessel also could be used in context of other types of subsea wells, for example water or gas injection wells.
It is understood that a floating vessel will be subjected to vertical and horizontal (pitch and roll) movement due to the action of the natural environment such as wind and the waves of the sea (or a lake), which in turn introduces a challenge with respect to equipment utilized during operations carried out on the floating vessel. Such operations may include, but are not limited to drilling, completion, well testing, and well intervention. During operation at sea, said equipment will be subjected to vertical movement unless compensated for such movement.
As a floating vessel moves up and down in response to the waves, e.g. a drill string and a drill bit extending down below the vessel from a load-bearing structure, such as a top drive located within a drilling rig, will also move up and down. As it is essential that the weight on the drill bit, i.e. the downward force applied to the bit, is kept as constant as possible, such up and down movements of the drill bit are undesirable and provide for inefficient drilling progress which is counterproductive. Heave will remove weight from the drill bit as the rig moves up in conjunction with the high crest of a wave, while weight will be added to the drill bit as the rig moves down into the low point between two waves. Should hydrocarbons start to flow from a reservoir and into a wellbore being drilled, a valve arrangement is utilized to prevent such hydrocarbons from discharging into the natural environment and onto the floating drilling vessel. Such a valve arrangement is commonly referred to as a Blow Out Preventer (BOP), which is capable of sealing around, or cutting and sealing above, a drill pipe cut by shear rams in the BOP.
In other operations, which may include well testing and well intervention, e.g. wireline operations and coiled tubing operations, several sections of a high pressure tubular, commonly referred to as workover riser, are connected between equipment located at the seafloor, such as a subsea wellhead or a subsea Christmas tree, and the floating drilling vessel. The workover riser provides a barrier element for allowing control of pressurized hydrocarbon fluids present in the reservoir, and hence in the wellbore. A subsea valve arrangement, such as a subsea BOP, is also utilized in such operations to provide a system capable of sealing the well in case of an uncontrolled discharge of hydrocarbons from the reservoir. During such operations, hydrocarbon fluids may be present throughout the wellbore and the workover riser, and discharge at surface rig level is typically prevented by means of a valve arrangement located at the surface, commonly referred to as a surface flow tree. A surface flow tree, or similar equipment attached to a workover riser, extending upwards from equipment located on the seafloor to the rig, is usually supported by, and kept in tension by, the top drive and drawworks forming part of the drilling rig on a floating drilling vessel. Various types of lifting arrangements are utilized to connect the surface flow tree to the top drive and to hold the workover riser in tension as required to prevent high loads from acting on the equipment on the seafloor. Such lifting arrangements may include, but are not limited to, rigid bails, tension frames, soft slings, and backup heave compensation systems. A backup heave compensation system is disclosed in U.S. provisional application Ser. No. 61/480,239 and is referenced herein for informative purposes.
Well completion involves the use of production tubulars, which typically extend downwards from the wellhead and the Christmas tree to the producing zones bound by the reservoir(s) targeted by the well(s). Some parts of a completion operation will require equipment to be in tension in a manner similar to that described above. This may comprise setting the upper lock and seal mechanism of the production tubular, commonly referred to as a tubing hanger, inside the well-head. At this point, a landing string, which is typically made up of several sections of tubular, such as drill pipe or workover riser, will be connected to said tubing hanger at the wellhead and to the top drive at the floating drilling vessel via said lifting equipment. Similar to the description above, the weight of the system is controlled by holding said landing string in tension, thereby maintaining a known force at the level of said tubing hanger.
In operations requiring coiled tubing it is necessary, as mentioned above, to utilize a lifting arrangement capable of maintaining tension in the tubular extending from the wellhead to the floating vessel, such as a workover riser system, to prevent high loads from acting on the equipment on the seafloor. The lifting arrangement must be of a size such that coiled tubing equipment, such as a coiled tubing BOP, coiled tubing dual stripper arrangement and coiled tubing injector head, can be fitted and supported within the lifting arrangement. Furthermore, it is beneficial and in some instances a requirement that the coiled tubing equipment is transported to and from the lifting arrangement by means of lifting devices such as winches and/or hoists integrated in the lifting arrangement. Based on this, it is common practice to utilize tension frames with integrated lifting devices to accommodate for coiled tubing equipment required to execute said operations. The complexity of such tension frames are continuously evolving with respect to functionality integrated in such frames. Such functionality may include but is not limited to lifting devices, such as winches and hoists, manipulator devices utilized to guide equipment being lifted, advanced platform devices comprising means for vertical and horizontal adjustment of equipment such as the coiled tubing injector head, and adjustable work platform devices to accommodate for risk reducing measures during operational sequences and maintenance of equipment. Additional functionality is not merely advantageous as complexity and weight increases, and in some situations limits overall applicability of a tension frame due to said complexity and amount and severity of handling operations required to rig up the tension frame and furthermore change from one mode to another, such as to change from a coiled tubing mode to a wireline mode. Additionally, complex and time consuming operations are required onshore to prepare such tension frames for coiled tubing mode. In situations requiring coiled tubing capability on a floating vessel it is normally, as a minimum, required to utilize wireline equipment prior and after the coiled tubing intervention, hence it is required to alternate between wireline and coiled tubing modes several times. Based on this, it is commonly understood that the added functionality described above introduces disadvantages and increases the risk to personnel and equipment during intervention operations executed by means of tension frames, coiled tubing equipment, and wireline equipment.
In accordance with prior art intervention operations, such as for wireline and coiled tubing operations are executed by means of an intervention frame, such as a coiled tubing tension frame. The tension frame is utilized as a lifting arrangement connected to a load bearing unit in top, such as a top drive, and a surface valve arrangement in bottom, such as a surface flow tree or wireline adapter, further connected to a tubular, such as a workover riser or drilling tubular, extending from the floating vessel to equipment located on the seafloor. Hence, the tension frame and top drive is organized in a manner to hold the weight of said surface flow tree and said tubular, and furthermore ensure that the tubular is in tension to prevent high loads from acting on the equipment on the seafloor. In early configurations of such tension frames, it was common that one lifting device, such as a winch or hoist, was included in a top load bearing member, such as a beam, of the tension frame, which in turn was utilized to lift intervention devices, such as coiled tubing BOP and injector head, from a deck to the tension frame and landed onto a tubular member, such as a x-over/adapter, extending from a said surface flow tree or wireline adapter into the tension frame and also in reverse order in conjunction with removing the coiled tubing equipment from the workover riser stack and tension frame to be landed back onto the deck. The x-over/adapter extending from said surface flow tree or wireline adapter is commonly utilized as the mechanical interface towards a lower load bearing member, such as a beam arranged with such an mechanical interface, of the tension frame such that all forces are maintained by this said mechanical interface.
During recent years several intervention frame concepts have evolved, comprising more advanced functionality related to handling of intervention devices, such as coiled tubing BOP and injector head. These more advanced tension frames typically comprise two or more handling winches/hoists attached to a top load bearing member, such as a top beam, an injector head handling apparatus, such as a platform apparatus, attached to at least two parallel guides, such as tension frame legs, forming a substantially vertical tensioning frame, a manipulator device, adjustable work platform devices, and a lower load bearing member, such as a beam, with an integrated mechanical interface towards a tubular such as a x-over/adapter, extending from a said surface flow tree or wireline adapter into the tension frame. The winches/hoists are typically split into various categories with respect to rated specifications, where a large version winch/hoist is utilized to lift the coiled tubing BOP and injector head into/out of the frame during rigging, while smaller winches/hoists are utilized to handle and rig up smaller equipment such as devices dedicated for purposes of the work in a well, such as bottom hole assemblies used for the actual operation in a well. The platform apparatus defines a landing point for a coiled tubing injector during rigup, whereupon after landing the injector head is moved horizontally and vertically by means of functionality part of the platform apparatus and/or said tension frame. The manipulator device is included to function as a guide to prevent loads hanging from winches/hoists from moving during handling. Adjustable work platforms are included to ensure safe working areas for personnel during operation and maintenance of equipment that is part of the intervention operation executed by means of the intervention frame and intervention devices described herein.
Despite of having some advantages, the recent technological evolvements related to coiled tubing tension frames introduce several disadvantages. The platform apparatus mentioned above requires hydraulic and/or mechanical systems to enable horizontal and vertical movement from a remote location. This functionality comprises several moving and fixed devices which add weight and complexity to the total system during handling, and additional control functions and related hydraulic conduits and/or electric conduits must be part of the tension frame during handling. Additionally, since the platform apparatus is a part of the tension frame prior to lifting intervention devices, such as a coiled tubing injector head, it is necessary to lift the injector head to a certain height prior to moving the load towards center to ensure clearance between the injector head and said platform apparatus prior to landing the injector head onto the platform apparatus, which in turn impose a large working angle onto the winch/hoist wire/chain during handling. Furthermore, the platform apparatus introduces a large sized piece of equipment which is not required for other intervention operations to be executed, such as wireline work, such that it would be beneficial to remove the platform apparatus prior to executing said wireline operations. However, due to the complexity involved with removing the platform apparatus from the tension frame in a rigged up and hence operational position, it is common to leave this as part of the tension frame during said wireline operations further implying non-optimal working environment during said wirleline operations.
It is commonly accepted that weight and complexity of an intervention frame should be limited to a minimum during handling to reduce risk of failure and consequences related to potential accidental situations.
GB 2 418 684 B discloses an apparatus and a method for protecting against problems associated with handling a coiled tubing injector head within a coiled tubing tension frame. The publication discloses a platform apparatus adapted for connection with an intervention frame, the platform apparatus comprising a supporting member, such that in use, the platform apparatus is connected to the intervention frame and the supporting member is shaped or otherwise adapted to support an intervention tool such as a coiled tubing injector. Thus, it is possible to stow an injector head on the intervention frame during use of the frame for other purposes, such as wireline. The publication further specifies that this apparatus and method will significantly reduce the amount of time required for changeover from coiled tubing intervention to wireline intervention. The publication further specifies that in preferred embodiments, the platform apparatus is rotatably connected to the frame and also comprises a turntable. Preferably the platform apparatus can rotate around the frame in a first direction whilst the turntable apparatus rotates in the opposite direction thus maintaining the direction of any coiled tubing towards a V-door provided in the derrick, regardless of the rotational position of the platform apparatus. The invention describes a method for handling a coiled tubing injector head inside an intervention frame, which in turn can be rotated to the side of the intervention frame to create free space for a wireline operation. However, one skilled in the art will recognize disadvantages and operational limitations as it is disadvantageous to position a large load, as represented by a coiled tubing injector head, on the side of an intervention frame structure, as this will generate an uneven force distribution and related bending moments in an intervention frame subjected to movements as generated by movements of the floating drilling vessel as inflicted by the natural environment. Furthermore, the disclosed apparatus illustrates a system where the platform apparatus is mounted as a part of the intervention frame prior to lifting the injector head, further meaning that it is necessary to lift the injector head to a certain height prior to moving the load towards center to ensure clearance between the injector head and platform apparatus prior to landing the injector head onto the platform apparatus, which in turn impose a large working angle onto the winch/hoist wire/chain used during handling.
Further, NO 322006 (B1)/U.S. Pat. No. 7,306,404 B2 also describes a platform apparatus being part of a handling device for well intervention on a floating vessel. The publications disclose a handling device for well intervention, the handling device being releasably connected, in an operative position, to a riser and to a heave compensator which is arranged to maintain a prescribed tensioning of the riser. The handling device comprising: a lower riser securing device; a substantially vertical tensioning frame provided with at least two parallel guides; a jacking table provided with an upper riser securing device; at least one tension-resistant connection between the tensioning frame and the heave compensator located there-above; the jacking table being movable connected to the at least two parallel guides, at least one of the at least two parallel guides including lifting screws for moving the jacking table along the guides in their, in the position of use, vertical extent, and the jacking table including hydraulic cylinders for moving the upper riser securing device in a horizontal direction along at least one axis of movement. One skilled in the art will recognize that the disclosure describes an intervention frame, such as a tension frame, with a moveable jacking table comprising a device and method for clamping onto a tubular, such as a riser, to function as a method for rigging tubular riser sections within the intervention frame, by means of vertical and horizontal displacement of the jacking table. One skilled in the art will furthermore recognize that the jacking table may function as a landing platform for a coiled tubing injector head, and furthermore provide means for handling said injector head in both vertical and horizontal directions. However, in the same manner as explained for the disclosed publication GB 2 418 684 B, the disclosed apparatus and method in publications NO 322006 (B1)/U.S. Pat. No. 7,306,404 B2 describes a system where the platform apparatus, by means of the jacking table, is mounted as a part of the intervention frame prior to lifting the injector head, further meaning that it is necessary to lift the injector head to a certain height prior to moving the load towards center to ensure clearance between the injector head and platform apparatus prior to landing the injector head onto the platform apparatus, which in turn impose a large working angle onto the winch/hoist wire/chain used during handling.